In fact, the development of wideband wireless networks has been so successful that several standards coexist. Amongst the various standards may be mentioned HYPERLAN or IEEE802.11A, which operate in frequency bands situated around 5 GHz, but also IEEE802.11B and IEEE802.11G which operate in frequency bands situated around 2.4 GHz.
In the field of mobile devices, it is desirable to be able to offer low-cost, compact products that can operate at one or the other of the frequencies with interfaces and signal processing circuits having the maximum functionalities common to the two frequencies. These products must offer a common antenna access for the two frequencies. Accordingly, the antenna used can be an antenna having a very wide frequency band, including the frequencies 2.4 GHz and 5 GHz, or an antenna having a double frequency band, namely separately covering two separate bands at 2.4 GHz and 5 GHz. However, such a system that allows the size and especially the equipment production cost to be minimized may suffer from noise and interference coming from the unused band.
Consequently, the present invention proposes an antenna that allows switching from one band of operation to the other according to the operating mode being used by the equipment and the effects of noise and interference coming from the other band to be minimized.